Various metal complexes comprising metal species and ligands are widely used as catalysts for organic synthesis reactions. Not only the metal species but also the ligand in the metal complex, which is an organic compound having a group (coordination group) having lone pair electrons capable of coordinating to the metal species plays an extremely important role, is known as a factor for the expression of the performance and activity of such a catalyst. Especially, metal complexes with tridentate ligand having an imino group as a coordination group in the molecule are known to exhibit high catalytic activities in, for example, hydrogenation reactions of carbonyl compounds, dehydrogenation reactions of alcohols, and the like, and also the hydrogen atom on the imino group is known to exert great influences on the expression of activities in these catalytic organic synthesis reactions. Known examples of such a tridentate ligand include N,N-bis(2-phosphinoethyl)amine, and it is reported that ruthenium complexes with the tridentate ligand function as excellent catalysts in hydrogenation reactions of esters (Patent Documents 1 to 4 and Non-Patent Documents 1 to 3). N,N-bis(2-diarylphosphinoethyl)amines used as a ligand can be synthesized easily by introducing phosphino groups as the coordination groups to N,N-bis(2-chloroethyl)amine as a substrate. On the other hand, in the case of synthesizing N,N-bis(2-dialkylphosphinoethyl)amine having an alkyl group substituted on phosphorus, since the yield is low in the foregoing method, there has been developed a method of protecting an imino group of N,N-bis(2-chloroethyl)amine with a trimethylsilyl group to provide N,N-bis(2-chloroethyl)trimethylsilylamine and introducing dialkylphosphino groups at an extremely low temperature (Non-Patent Document 4). However, this production method has problems such that purification is difficult because N,N-bis(2-chloroethyl)trimethylsilylamine of a substrate is decomposed during distillation, that an expensive silylating agent is necessary, that operation at a cryogenic temperature is necessary, and that troublesome operation such as degassing operation is necessary because N,N-bis(2-dialkylphosphinoethyl)amine obtained is unstable to air.
As a method for producing a ruthenium complex containing N,N-bis(2-dialkylphosphinoethyl)amine as a ligand, a production method using RuHCl(CO) (PPh3)3 as a precursor and the like are known; however, this method has disadvantageous problems for industrialization such that a troublesome operation is required because the ligand is unstable to air, and that reaction at high temperature for a long time is required.
Thus, there has been desired a method for producing N,N-bis(2-dialkylphosphinoethyl)amines and a ruthenium complex with the N,N-bis(2-dialkylphosphinoethyl)amine, which is suitable for industrialization and is practical, and does not have the problems as described above, that is, which allows short production process, mild reaction conditions, and easy production with high yield.